Phosphorylation of the synaptonemal complex protein SYP-1 promotes meiotic chromosome segregation

Chromosomes that have undergone crossing over in meiotic prophase must maintain sister chromatid cohesion somewhere along their length between the first and second meiotic divisions. Although many eukaryotes use the centromere as a site to maintain cohesion, the holocentric organism Caenorhabditis elegans instead creates two chromosome domains of unequal length termed the short arm and long arm, which become the first and second site of cohesion loss at meiosis I and II. The mechanisms that confer distinct functions to the short and long arm domains remain poorly understood. Here, we show that phosphorylation of the synaptonemal complex protein SYP-1 is required to create these domains. Once crossover sites are designated, phosphorylated SYP-1 and PLK-2 become cooperatively confined to short arms and guide phosphorylated histone H3 and the chromosomal passenger complex to the site of meiosis I cohesion loss. Our results show that PLK-2 and phosphorylated SYP-1 ensure creation of the short arm subdomain, promoting disjunction of chromosomes in meiosis I.

在减数分裂前期发生过交换的染色体，必须在第一次与第二次减数分裂之间的染色体全长区域维持姐妹染色单体黏着（sister chromatid cohesion）。尽管许多真核生物以着丝粒（centromere）作为维持黏着的位点，但全着丝粒（holocentric）生物秀丽隐杆线虫（Caenorhabditis elegans）则会生成两个长度不均等的染色体结构域，分别命名为短臂与长臂，二者依次成为减数第一次分裂（meiosis I）与减数第二次分裂（meiosis II）时黏着解除的第一、二位点。目前，学界对如何赋予短臂与长臂结构域差异化功能的分子机制仍不甚明晰。本研究证实，联会复合体（synaptonemal complex）蛋白SYP-1的磷酸化是形成此类结构域的必要条件。在交换位点被确定后，磷酸化SYP-1与PLK-2会协同富集于短臂区域，并引导磷酸化组蛋白H3（phosphorylated histone H3）与染色体乘客复合体（chromosomal passenger complex）定位至减数第一次分裂时黏着解除的位点。本研究结果表明，PLK-2与磷酸化SYP-1可保障短臂亚结构域的形成，进而促进减数第一次分裂过程中的染色体分离。